G E O M A T I C A THE GPS ATTITUDE, POSITIONING, AND PROFILING EXPERIMENT FOR THE ENHANCED POLAR OUTFLOW PROBE PLATFORM ON THE CANADIAN CASSIOPE SATELLITE Don Kim and Richard B. Langley Department of Geodesy and Geomatics Engineering, University of New Brunswick The CAScade, Smallsat and IOnospheric Polar Explorer, or CASSIOPE, is Canada’s first multi-purpose small satellite, scheduled to be launched in 2011. It features two main payloads: the Enhanced Polar Outflow Probe, or e-POP, and Cascade. Together, they will achieve both a scientific and a commercial objective: e-POP will provide scientists with unprecedented details about the Earth’s ionosphere, thermosphere, and magne- tosphere, helping scientists better understand the cause and effects of potentially dangerous space weather, while Cascade will demonstrate a new high-capacity store-and-forward digital communications service. e-POP consists of eight scientific instruments, one of which is the GPS Attitude, Positioning, and Profiling experiment (GAP). GAP employs five dual-frequency GPS (Global Positioning System) receivers and associ- ated antennas to provide the e-POP payload with high-resolution spatial positioning information, flight-path velocity determination, and real-time, high-stability timing. In addition, by measuring the arrival times of the Don Kim GPS signal wave fronts at each antenna against a very stable time base, the relative range between antennas
[email protected] can be determined, yielding real-time spacecraft attitude determination. The GAP receivers are slightly modified, commercial, off-the-shelf units that required a series of tests before they could be considered capa- ble for use on an orbiting spacecraft.